Sage is a great energy cleanser. It cleanses negativity and entities and clears the aura.
Smudging is the cleansing of auras and energies of a person or space. Lighting the bundle and using the smoke around the person or space along with visualizing the removal of negative energy forms the ritual of smudging.
Using a smudging tool is part of many wiccan/pagan Traditions. The burning of herbs for emotional, psychic, and spiritual purification is also common practice among many religious, healing, and spiritual groups. In theory, the smoke attaches itself to negative energy and as the smoke clears it takes the negative energy with it, releasing it into another space where it will be regenerated into positive energy.